emissions trading has been on the cards for years and years. So aviation comes in as a part of phase 2 of the scheme. All large industries will eventually be a part of it. The aim is to cap carbon emissions at x number of million tonnes in europe every year. Industries that can clean up can sell their permits to industries that can't. It's not just a tax on aviation it's an attempt to do something about carbon emissions in all industries in Europe.
BA have been a part of the UK-ETS for a few years. It's an attempt to meet the kyoto targets. Whether it's the answer to carbon emissions i don't know, but it's a start.